Spark plug



May 19, 1942 H. M. BREWSTER SPARK PLUG Filed May 31, 1940 KZ/ ,l. a V6 m2 Patented May 19, 1942 UNITEDSTATES PATENT OFFICE SPARK PLUG Herbert M. Brewster, Chicago, Ill.

Application May 31, 1940, Serial No. 338,084

1 Claim.

My present invention pertains to certain betterments and improvements in spark-plugs, such as are commonly used with internal-combustion engines for ignition purposes.

One aim of this invention is the provision of a spark-plug which can be made and sold for a lesser price than heretofore.

A further purpose of this invention is to supply a spark-plug which will be maintained cooler in action and service than has formerly been feasible.

An added object of the invention is to provide a spark-plug incorporating less metal than has been customary. l

A salient feature of the novel spark-plug is the elimination from its construction of the usual hexagonal portion of its metal-member.

designed to project into the cylinder or other part I of the motor with which the spark-plug is to be associated, the opposite protruding end of such central rod or electrode being shaped and designed for connection with an electrical-conductor or insulated-wire, all as is well understood in the art.

Such porcelain-member is mounted in gaspressure-tight relation in a hollow metal-body l3 externally screw-threaded at one end, as shown, for screwing it into a hole in the motor-block as is customary, and the pressure-tight mounting of the insulating-member is effected by gaskets l4 and I5 interposed between the member H and A further goal of the invention is the produc- Y tion of a spark-plug of shorter length than has been the practice.

A supplementary mark of the invention is the making of a spark-plug in which the work required in its manufacture is reduced to a minimum.

A design of the invention is to supply a sparkplug with a reduced-size porcelain or comparable insulating element.

An auxiliary end of the invention is the making of a spark-plug from an original piece of metal stock of cylindrical form.

Other objects and advantages oi the invention will become apparent to those smiled in the art from the following detailed description of a preierred embodiment thereof.

To enable those acquainted with this craft and industry to understand the invention and its ac= companying advantages, a present preferred embodiment thereof has been illustrated in the accompanying drawing, and, for simplicity, like reference numerals have been employed to designate the same parts in the three figures of such drawing.

In this drawing:

Figure l is an elevation of the new spark-plug;

Figure 2 is a central longitudinal section through such plug; and

Figure 3 is a cross-section on line 3-3 of Figure 1.

I3 by which they are permanently maintained in that relation by crimping or spinning down the metal of element l3 around and on to the element I I as at It, whereby the two parts become a unit in effect, the opposite end of the metallic-body carrying an electrode H in proper spaced relation to the insulated electrode l2 as is common practice.

From the drawing, it will be seen that this metal-body is cylindrical, having nothing comparable to the ordinary hexagonal-portion by means of which, with a wrench applied thereto, the spark-plug may be screwed into place and unscrewed therefrom.

Such metal-body is, therefore, shorter than that of the usual plug and hence maintained relatively cooler, in that a greater percentage of the metal element is in closer relation to the watercooled jacket of the engine, with the result that the plug as a whole is maintained at a lower temperature than one having a substantial portion exposed to the air rather than to the more eiiicient and effective water-jacket of the motor.

In order that this new plug may be easily and readily screwed into place in the motor, and removed therefrom when required, the opposite sides of the round porcelain-member ii are made fiat at it, Hi for the application of the wrench direct to the porcelain so that the entire plug may be screwed in the motor or unscrewed therefrom by the wrench acting through the porcelainmember.

While, at first blush, this method of screwing the spark-plug into the engine and its unscrewing or removal therefrom by means of a tool applied directly to the porcelain or other comparable insulating agent may appear to be untenable or indiscreet, experience nevertheless has demonstrated that it is quite practical and without substantial danger of breakage of the porcelainmember especially when it is borne in mind that spark-plugs should not be screwed into place with undue force or pressure.

I am acquainted with earlier spark-plugs in which screw-threaded porcelain or other electrically non-conductive members had accessible hexagonally-shaped sections by which, in connection with an applied wrench, they could be screwed into the metal-body of the plug, but, in

each such instance, so far as I know. the metal-- member also had an angular or hexagonal portion to which a wrench was fitted for screwing the plug into, and also for removing it from, the engine cylinder-wall.

Inasmuch as such porcelain-members were screwed into their metal-bodies, the former could not be used for unscrewing the plugs from the engine, since the porcelains would merely unscrew from their own metal-bodies leaving the latter in place in the engine, and, furthermore, no one heretofore, has conceived the idea of advantageously leaving off the flattened portions of the metal-bodies with dependence entirely on the porcelain-members for applying the whole plugs to and detaching them from the engine.

Those acquainted with this art will understand from the foregoing description and the accompanying illustration how the objects and aims of the invention heretofore specified have been attained in the new spark-plug, one of these residing in the fact that round or cylindrical, rather than hexagonal, metal stock may be used in the automatic machines which produce the metalbodies of the plugs.

The invention is not necessarily limited and restricted to the precise and exact details of structure shown and described and modifications within reasonable limits may be resorted to without departure from the heart and essence of the invention as defined by the appended claim and without the loss or sacrifice of any of its substantial or material advantages accruing from employment of the invention.

.1 claim:

In an internal-combustion engine spark-plug of the type having a hollow metal-body at least a partially externally screw-threaded for mounting. in the engine, an electrically non-conductive.

member at leastpartially accommodated in said body in gas-pressure tight relation therewith;

said body and member being permanently fixed as a whole may be screwed into position in the engine and unscrewed therefrom.

HERBERT M. BREWSTER. 

